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TED STATES PATENT oTTTos.

HENRY ROBERT POWER, OF FALLS, YORK, ASSIGN'OR TO THE CARBORUNDUM COMPANY, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF PENNSYLVANIA.

No Drawing.

To all whom it may concern:

Be it known that I, HENRx ROBERT PownR, a citizen of the United States, residing at Niagara Falls, in the county of Niagara and State of New York, have invented a new and useful Abrasive Wheel, of which the following is a specification.

My invention relates to the field of abrasive wheels, and more particularly to an improvement in open or porous abrasive Wheels in which the bond employed to hold together the particles of abrasive materials is a silicate.

My invention is designed to improve the construction of such wheels in such a way as to greatly increase their efliciency.

Abrasive wheels to which my invention relates, are made up of an abrasive material, such as carborundum or carbid of silicon, an aluminous abrasive commonly known as emery, aloxite, and corundum, held together by aceramicbond. In such wheels, the bond maybe silicate of soda which is mixed with the abrasive grains, together with certain other chemical compounds, and heated to a temperature suflicient to cause a reaction between the silicate and these other chemicals. This gives a hard porous mass in which the abrasive grains are held securely in place. Such wheels are known as silicate of soda wheels. Or the bond may be clay, together with other mineral silicates such as feldspar, etc. In such wheels the bond and grain are mixed and heated in a kiln until the bond melts or fuses. This gives upon cooling a hard, porous mass, and such a wheel is known commercially as a vitrified wheel.

Both of the types of wheel above described are porous and in the grinding process these pores become filled with particles of the material being ground, thus covering over the sharp. cutting edges of the abrasive grains and preventing proper clearance for the cutting points. Also in the grinding process the abrasive particles become worn, lose their sharp edges and become too smooth for effective work. A wheel which is thus dull or loaded with the particles of ground material must be frequently reduced with a dressing tool to expose new cutting surfaces, which is a laborious, expensive operation.

ABRASIVE WHEEL.

Patented July 15,19i9.

Application filed August 27. 1918. Serial No. 251,645.

To increase the efficiency of a porous wheel as above described, it has been customary in certain classes of work to fill the wheel with a material that becomes soft and fluid at the grinding temperature. A substance commonly used for this purpose. is ordinary parafiin wax. Paraifin wax is, to a certain extent, satisfactory in accomplishing this purpose; but, for certain classes of grinding, the wheel becomes quite hot and melted parafiin is thrown out of the wheels before the grinding temperature is reached.

It thus fails to accomplish its purpose in such grinding operations. Moreover, the wheel may get out of balance, and if the grinding process gives much heat, the paraffin fumes, and the operation becomes disagreeable to the workman.

In accordance with my invention I fill the pores of the wheel with a mixture of a paraffin wax and a high melting chemical compound, which compound is known chemically as polymerized benzofuran or paracoumarone. This compound, which is a coal-tar distillate, is sold commercially under the names of coumarone and paracoumarone though they are practically identical in their physical and chemical properties.

The substance known chemically as benzofuran or coumarone is definite and has the formula C H O shown structurally thus naphtha. This in turn fer to use in my process, although I do not limit myself to this particular method of obtaining paracoumarone. The structural formula of paracoumarone is shown as follows, being made up of two molecules of coumarone:

It is possible that more than two molecules unite to form even higher molecular aggregates.

There are several commercial grades of paracoumarone, some being highly refined and odorless, tasteless and almost colorless. Others have a characteristic light yellow to dark brown color. The grades that are hard at ordinary temperatures are brittle. Others are tough and cold flowing at ordinary temperatures. The melting points of different grades run from degrees centigrade to 110 degrees Centigrade. The specific gravity is about-'1.1 in all grades. On heating, paracoumarone melts, gives a pleasant sweetish odor and on cooling again it is found to have lost none of its former chemical and physical properties.

The coal-tar distillate, paracoumarone, is practically inert; it has no saponification number, no acid number, it is insoluble in alcohol, and dissolves readily in solvent naphtha. With an alkali it yields no lather. Furthermore, it oxidizes very slowly, even .in the presence of strong oxidizing agents like nitric acid.

In the application of this mixture to the porous wheel I find it best to heat together the parafiin Wax and coal-tar distillate, paracoumarone, until the mixture is a homogeneous mass, and then to dip the wheel therein. It is not advisable to dip the wheel in the separate melted materials, because such a process would fail to give homogeneity in the mixture and would not permit of a control of-the amount of each material used.

In the carrying out of my invention, 1 have found that the ordinary impregnating machines may be used. In short, the process consists in placing the heated porous wheel in a closed apparatus and adding the melted mixture of paraffin wax and paracoumarone mixed in the proportions best suited for the particular purpose to which the finished wheel is to be applied. The mix is heated with coils in the machine and at the same time the pressure inside the machine is reduced to a partial vacuum to fa cilitatethe proper impregnation of the wheel with the fluid mixture. It is quite essential that the filler become uniformly distributed in order that the wheel may not be out of balance in the grinding operation. The process of impregnation usually occupies 25 minutes which is a suflicient length of time for practically all the Voids of the wheel to become filled with the mixture. On removing the wheel is trued and on cooling, the homogeneous mixture solidifies within the voids of the porous wheel. The pores may be wholly or partially filled with the mixture, and the term filled as used herein and in the claims is to be so understood.

Having thus described and identified the coal-tar distillate which I add to paraffin wax and having explained the process of adding the mixture to the wheels, 1 shall now explain the peculiar advantages resulting from the use of the mixture over the use of paraffin alone.

Paraffin wax melts at a temperature of less than 60 degrees centigrade. The several grades of the coal-tar distillate paracoumarone melt at various temperatures, but I prefer for my purpose to use the higher melting grades whose melting points are from 100 degrees centigrade to 110 degrees centigrade. If a certain amount of paracoumarone be added to paraffin wax, the melting point of the mixture is raised above that of wax. The exact grade which 1 use and the exact amounts of each grade depend on the desired melting temperature of the mixture.

If we add to the porous abrasive wheel an admixture of the wax and paracoumarone, a higher grinding temperature may be reached before the filler begins to flow and leave the wheel than was possible when paraffin alone was used as a filler. It is possible to so regulate the proportions of wax and paracoumarone that the admixture does not leave the wheel before the grinding temperature is reached. The purpose for which the admixture is added is thus accomplished, for the particles of ground metal cling to the melted mixture of wax and paracoumarone instead of filling the wheel. Loading is thus prevented. Moreover, the wheel remains true and does not get out of balance because the melted admixture does not fly out of the wheel too soon, during the grinding process.

The exact proportions of wax and paracoumarone mixed together depend on the temperature of the grinding operation and this is a variable factor. In some cases of grinding where a very high temperature obtains, a high melting mixture of the wax and paracoumarone is desirable. In other cases lower temperatures are found to result from the grinding operation, hence a different mixture must be used.

Moreover the addition of paracoumarone to paraflin for use in porous wheels has advantages apart from the effect on th melting temperature. Paracoumarone 1s brittle andadds brittleness to the mixture. This is a decided advantage for the brittle filler is easily pushed or knocked ofl during thegrinding process and does not become gummy, interfering with the efiiciency of the grinding operation.

I find that in the mixture used for filling the voids of a porous Wheel, ceresin or ceresin wax obtained from the crude mineral ozocerite, will act equally as well-as paraflin in the mixture.

Havingthus described my invention, what I claim as new and desire tosecure by Letters Patent is I claim:

1. An abrasive wheel comprising abrasive particles united by a silicate binder to form a porous structure and having the voids thereof filled with a mixture of mineral wax and the coal-tar distillate paracolumarone known chemically as polymerized benzofuran.

2. An abrasive wheel comprising abrasive products united by "a silicate binder to form thereof filled with .a mixture of wax and the bond, and having its voids filled with a mix- I ture of wax and a substance which raises the melting point of the wax and increases its brittleness.

bond, and having its voids filled with a mixture of Wax and a polymerized coal tar distillate having a'higher melting point than the wax.

6. An abrasive wheel having a ceramic bond, and having its voids filled with a mixture of wax and paracoumarone.

7. A11 abrasive wheel having a ceramic bond, and having its voids filled with a mixture of wax and a polymerized substance of the coumarone group having 'a higher melting point than the wax, the melting point of the mixture being sufficiently below to cause it to melt at grinding temperatures. I

In testimony whereof I have hereunto set my hand.

HENRY ROBERT POWER.

. 40 5. An abrasive wheel having a ceramic I 

